GB904732A - Process for hydrogenating aromatic hydrocarbons - Google Patents

Abstract

The hydrogenation of aromatic hydrocarbons is effected at superatmospheric pressure and not more than 427 DEG C. with hydrogen in the presence of a catalyst comprising an alumina-containing support containing minor proportions of a platinum group metal and an alkali or alkaline earth metal. The aromatic hydrocarbon may be a benzene of alkyl benzene or naphthalene. The catalyst support may contain minor amounts, with respect to the alumina, of silica, titania, zirconia and boria and may contain 0.1-2% of platinum, palladium, ruthenium or rhodium and up to 5%, preferably 0.01-0.7% of caesium, lithium, rubidium, sodium, magnesium, calcium, barium and/or strontium; a halogen may also be present. The catalyst is prepared conventionally by impregnation, drying and calcining. The aromatic compound is preferably treated in three or more reactors containing equal amounts of catalyst. The feed, e.g. benzene, is split into equal portions each of which is fed to a reactor; to the first reactor is also fed a cyclohexane recycle in an amount of 0.5-5 mols per mol of total benzene charge and sufficient hydrogen at 6.8-68 atmospheres pressure to leave at least 4 mols per mol of hydrocarbon in the product effluent. The feed to the first reactor is heated and the effluent from each reactor is mixed with the further benzene feed and cooled before passing to the next reactor. The total benzene charge to the total catalyst is fed at a rate of 1-5 vol./vol./hr. Unreacted hydrogen is separated, mixed with fresh hydrogen and treated to remove hydrogen sulphide by washing with aqueous caustic soda and water. The hydrogen is thus saturated with water which may be present in an amount up to 1% mol of the aromatic hydrocarbon. The catalyst is not poisoned by sulphur which may be present in the feed in amounts up to 3 p.p.m. The product contains less than 0.1% mol of aromatic hydrocarbon.